Can solar panels be made without silver?
Most solar panels today use silver for wiring because it's highly conductive. This is expensive, but there are ways to make panels without this pricy metal.
If you’ve ever seen a solar panel up close, you might have noticed thin little wires running across each cell.
Those little wires do the important job of carrying electrons (electricity) generated by the solar cells into thicker main wires of the panel. You might know from high school science that thin wires have higher resistance, which means they lose more electricity as heat. In a solar panel, that means lower efficiency.
That’s where silver comes in. Silver has the highest electrical conductivity of any metal: it’s 5.7% more conductive than copper.
While that might seem like a pretty small improvement, it’s large enough to make the high cost of silver worth it. But solar panel manufacturing is competitive, so companies are looking for ways to reduce this cost.
Why reduce silver costs at all?
Solar panels are already pretty cheap, and upgrading factories with new manufacturing processes is expensive. So why bother to reduce silver costs at all?
One of the main reasons is that silver is a precious metal, and the cost can fluctuatate. In fact, one of the things that’s driving the cost of silver is solar panels. Demand for solar energy has grown exponentially and will continue to increase in the future: President Joe Biden has set a goal of 500 million solar panels in the next five years.
With so much demand, the cost of silver is expected to increase, injecting uncertainty into the bottom line of panel manufacturers around the globe.
Companies don’t like that kind of uncertainty, so reducing or eliminating silver in solar cells is a worthwhile goal.
How is silver used in solar cells?
A typical solar cell has fine wires on the front. These wires are actually screenprinted, in a process akin to one used to make your favorite concert t-shirt.
The thicker wires are called busbars and the thinner ones are fingers. They look like this:
Because the wires are so thin, electrical resistance becomes important. This is where silver is used to reduce electrical resistance and improve the efficiency of the panel.
The silver metal is takes the form of a paste and is screen printed onto the front of the cell. In total, a 60 cell solar panel might use somewhere in the neighborhood of 8 grams of silver. At the current market price of about $0.80 per gram, that’s about $6.40 worth of silver in every solar panel.
That’s really not a lot, but solar panel manufacturing is a highly competitive, global industry. Margins are tight and every penny counts. That’s why reducing the use of this precious metal is a goal of many companies.
Can silver be reduced in solar panels?
One of the ways to use less silver in solar cells is to make the fingers as thin as possible through manufacturing improvements. They are already extremely thin: 30 micrometers wide and tall in some cases.
But the German lab Fraunhofer ISE has worked on a screen printing process that can reduce that to 19 micrometers, which will reduce the amount of silver used by around 30%. At the same time, the process improves cell efficiency, so it’s a win-win. Hopefully this manufacturing process will eventually make into commercial use soon.
Back contact cells can eliminate silver entirely
Another way to eliminate silver is to develop rear contact or back contact solar cells. With this type of cell, the wiring is placed on the back of the cell rather than the front.
Because of this placement, the wires no longer block light from hitting the front of the cell. This means that the electrical conductivity of the wires is less critical, which allows manufacturers to use cheaper metals such as copper.
In fact Maxeon solar cells, which are used in SunPower panels, cover the entire rear of the cell with a sheet of copper:
While copper is also expensive, it’s still about 50 times cheaper than silver. This means that solar panel manufacturers can use a lot more copper with rear contact cells and still save money.
The LG NeON series is another popular solar panel that uses rear contact cells. Perhaps it’s no accident that these two companies make the highest efficiency panels and are competitors in the premium solar panel market.
Future innovations to reduce silver usage in solar panels
While it might seem like a simple change to move wires to the back, the normal tendency of a solar cell is for the electricity to flow out the front (the sunny side). Making rear contact solar cells work comes with their own manufacturing challenges and costs, which is why they’re limited to premium solar panels so far.
Still, there are always ongoing innovations when it comes to solar panels, and much research is currently dedicated to reducing or eliminating the use of silver. One prediction is that silver usage will be reduced by half by 2028 - a welcome development that will help solar panels continue to get better and cheaper.